This invention relates to a tension-compression stay comprising a synthetic resin tubular strut reinforced by fibers of high rigidity and force-introducing elements of metal fastened to the ends of the strut.
Such composite stays are used in all those situations in which high supporting capacity as well as a low weight are demanded simultaneously of the stay, as is, for instance, the case in the construction of aircraft or the like.
Hitherto known stays of this kind often consist of a cylindrical strut of fiber- reinforced synthetic resin material at each end of which there is fastened a force-introducing element in the shape of a metal bell having a lug formed thereon. The metal bell and the tube end each have mutually fitting tapered ends with conical fitting surfaces generated by the beveling treatment, which surfaces are glued together.
In these known stays, there are thus glued directly together two materials of such different kind as fiber-reinforced synthetic resin and metal. This may cause undesirable tensions in the glued region which considerably decrease the resistivity of the connection. Moreover, such conventional stays are still relatively heavy.
In another known kind of tension-compression stays the metallic force-introducing elements are integrated in the synthetic resin material tube, i.e., they are already built into the fiber structure and anchored therein when the tube is being produced. This known construction is of relatively expensive production and is moreover of the same critical nature vis-a-vis temperature changes as the type of stay described hereinbefore.
In the European patent application No. 0,149,979, of earlier priority, which corresponds to U.S. patent application Ser. No. 689,527 filed Jan. 7, 1985, there is disclosed stay which is improved over the previously described stays, and comprises a synthetic resin tube reinforced by carbon or aramide fibers and having bottle neck-like reduced diameter ends in each of which there is glued a hollow cylindrical pin having approximately the same properties of mechanical resistance and thermal elongation as the tube material, while eyebolt-shaped force-introducing elements of metal are screwed into the two pins. This mode of construction avoids or reduces undesirable tensions in the region of force-introduction.
Further embodiments of stays and shafts having fiber-reinforced tubular elements are described, for instance, in U.S. Pat. Nos. 4,050,827, 4,358,284, 4,421,497 and 4,433,933 as well as in European patent application No. 59,163, to which
U.S. patent application Ser. No. 347.403 filed Oct. 2nd, 1982 corresponds, and French patent application No. 2,496,836.